A calorie describes the amount of energy required to heat 1 gram of water by 1° Celsius. Throughout the day, we are constantly consuming energy (calories) from the foods and beverages we consume, while we are simultaneously burning energy (calories) as our bodies carry out metabolic processes to keep us alive and moving. The balance of our daily energy intake and expenditure is, intuitively enough, referred to as energy balance, and this is what largely dictates our changes in body composition.
We burn some amount of energy every single day, and unless we’re doing a pretty extreme fasting protocol, we consume energy (in the form of foods, beverages, and dietary supplements) as well. In simplified terms, energy balance refers to the relative daily balance between energy consumed and energy burned, and in the United States, we tend to discuss energy intake and expenditure in terms of calories.
In simplified terms, energy balance refers to the relative daily balance between energy consumed and energy burned
The word “calorie” brings us a little bit of confusion when we apply it to the nutrition world. The calorie is a very, very small unit of energy, so when we talk about energy intake or expenditure, we typically refer to kilocalories (1 kilocalorie = 1,000 calories), which are often shortened to “Calories” with a capital C. So, when someone indicates that they ate 2,300 Calories yesterday, they actually ate 2,300 kilocalories, which is 2,300,000 calories. You might also see people using kilojoules as a unit (1 calorie = 4.184 joules, 1 kilocalorie = 4.184 kilojoules).
We ingest our kilocalories in the form of macronutrients, which include carbohydrate, fat, protein, and alcohol. A gram of protein provides about 4 kilocalories, a gram of fat provides about 9 kilocalories, a gram of carbohydrate provides about 4 kilocalories, and a gram of alcohol provides about 7 kilocalories. As such, we can estimate our daily energy intake by summing the energy provided by our daily intakes of protein, fat, carbohydrate, and alcohol.
Just as we can partition our total energy intake into contributions from distinct macronutrients, we can also partition our energy expenditure into distinct compartments. As discussed in The Metabolic Adaptation Manual, total daily energy expenditure (TDEE) describes the total number of kilocalories we burn in a given day, and TDEE is made up of four components:
Basal Metabolic Rate (BMR; ~70% of TDEE in general population)
This describes the energy required to simply keep our body “on,” at rest, assuming we lay in bed all day without moving or eating.
Thermic Effect of Feeding (TEF; ~10% of TDEE in general population)
This describes the energy used in the process of eating, digesting, metabolizing, and storing food.
Exercise Activity Thermogenesis (EAT; ~5% of TDEE, depending on how much you exercise)
This describes the energy used during structured, intentional exercise.
Non-Exercise Activity Thermogenesis (NEAT; ~15% of TDEE, depending on your activity level)
This describes the energy used for any movement that isn’t purposeful exercise. This would include walking around your school or office, doing yard work, taking out the trash, and even fidgeting in your chair.
The approximate relative contributions of basal metabolic rate (BMR), thermic effect of feeding (TEF), exercise activity thermogenesis (EAT), and non-exercise activity thermogenesis (NEAT) to total daily energy expenditure in the general population
We have some magnitude of resting energy expenditure every single day, no matter what. On a typical day, we also do some activities of daily living (which contribute to NEAT), consume some food (which contributes to TEF), and we might also do some structured exercise (which contributes to EAT). If we knew the true energy cost of each category of energy expenditure, we could calculate our total daily energy expenditure by summing the values. When we’re consuming more calories than we burn, we’re in a calorie surplus, and when we’re burning more calories than we’re consuming, we’re in a calorie deficit.
It’s often said that the difference between the kilocalories we consume in our diet and the kilocalories we burn throughout the day dictate changes in body weight. As Menno Henselmans has previously explained in an article, this is a bit of an oversimplification. For starters, even if we track our energy intake with perfect accuracy, we don’t absorb every single calorie that might show up on a food label. In addition, there are fluctuating factors that influence our scale weight without influencing the actual amount of fat mass or lean tissue we have, such as transient fluctuations in water retention or fecal material in the gastrointestinal tract. Beyond that, the actual metabolizable energy content of fat mass and lean mass differ. In other words, breaking down one pound of lean mass yields a different amount of kilocalories than breaking down one pound of fat mass, and adding one pound of lean mass requires a different amount of kilocalories than adding one pound of fat mass.
So, when we have independent changes in fat mass and lean mass happening simultaneously, along with transient weight fluctuations related to total body water and gastrointestinal contents, it is theoretically possible to lose some weight or body fat while in a caloric surplus, or to gain some weight or body-fat while in a caloric deficit. So, in the interest of being nuanced, we should conclude that the net balance between the energy we absorb from our diet and the energy we burn dictates our change in body energy; how this change in body energy is partitioned into fat mass and lean mass will depend on the presence of adequate training and nutritional factors required to facilitate the accretion or retention of lean mass, and how this change in body energy influences total body weight will also be impacted by fluctuations in total body water and gastrointestinal contents. Now that we’ve got the technicalities out of the way, we can move onto the more practical stuff.
Manipulating Energy Balance
If we’re aiming to build muscle, we want to achieve an energy surplus, which has been shown to facilitate hypertrophy (after all, building muscle is an energy-intensive process). Having said that, we don’t necessarily want to go overboard with our surplus; the more excessive the surplus gets, the more unnecessary fat gain we’re inviting. If we’re aiming to lose fat, we want to achieve an energy deficit. Barring any precipitous and extremely atypical losses of lean mass, an energy deficit will put us in a position where we need to rely on stored fat to meet our body’s energy demands.
If we’re aiming to maintain our current body composition, then things are pretty simple; we just aim for an energy intake that keeps us at a pretty stable body weight, and we keep doing what we’re doing in terms of physical activity and training. If we’re trying to intentionally “recomp” (lose fat while gaining muscle), we have to focus a little more closely on threading the needle. We need to be eating enough to support muscle growth, while providing a robust training stimulus to promote that growth. Simultaneously, we have to keep energy intake low enough that our body needs to tap into stored fat for energy. We could theoretically be losing, gaining, or maintaining weight during a recomp, which all comes down to the relative rates of muscle gain and fat loss.
For example, an untrained person with plenty of body fat to lose could technically be recomping while losing body weight at a pretty steady clip; such an individual would have a pretty notable capacity to make beginner muscle gains while also achieving simultaneous fat loss. In contrast, a well-trained person with low body fat would not expect major weight fluctuations during a recomp, given that they have less fat to lose and pronounced muscle gains will be harder to come by. Rapid muscle gain is unlikely for drug-free lifters, particularly in the absence of a large caloric surplus, so it’s pretty rare to see marked weight gain during a recomp period.
No matter what body composition goal you're pursuing, it’s important to closely track and monitor energy balance as accurately as possible along the way. That's why MacroFactor continuously monitors your energy intake and a running estimate of your total daily energy expenditure so it can adjust your calorie and macro targets as you go.